The study was carried out to clarify the effect of several growth regulators (TIBA, TCA, IAA and GA) on the growth of potato stolons, and the following results were obtained : 1) Stolon showed a tendency to be turned into leafy stolon with TIBA, and to be maintained stoloniferous growth with IAA. 2) By means of bioassays of diffusible auxins (diffused by ethyl-ether), the stoloniferous stolon showed a higher activity at Rf value 0.4-0.5 (IAA) than the leafy one.